The present invention relates to digging slit trenches, and particularly to an endless chain for use in combination with a conventional chain saw drive unit for digging such trenches.
It is often necessary to dig trenches in which to bury conduits for electrical power hookups between an electrical power main cable and a house, or for similar burying of television antenna cables, telephone cables, water supply pipes, and lawn sprinkling system piping. Where such narrow cables and pipes are installed in an area which has been landscaped, it is preferable to provide a narrow trench of the required depth, instead of causing a much greater amount of destruction of existing landscaping by using shovels or conventional backhoes and other large power tools. Also, certain types of terrain, such as steeply sloped or terraced areas, are not well adapted for the use of large power tools.
Conventional ditching machines use wheels carrying shovels, and are also excessively large for many jobs. It is known to use a small, lightweight gasoline engine, however, to drive small trenching tools including endless chains carrying teeth designed to dig a narrow slit trench for use in situations such as those mentioned above.
Conventional chain saws provide a readily available small gasoline engine, combined with a clutch and a supporting bar structure normally used to guide and hold a saw chain carrying wood-cutting teeth. Such a saw chain is an endless loop driven by a sprocket connected through the clutch to the engine, so that the chain can be driven at high speed along the periphery of the saw bar.
While it is desirable to use such a power source to drive a chain designed for digging a narrow trench, such a chain saw drive unit typically requires significant amounts of modification in order for the previously known trenching chains to be driven. In particular, there is ordinarily too little clearance for digging teeth of a practical size, because of the closeness of the drive sprocket to the clutch provided on a chain saw drive unit. Additionally, the splinter shield provided around the drive sprocket of a chain saw usually provides too little radial clearance for trenching teeth of desirable size.
While some wear and damage to trenching teeth carried on a chain is inevitable, it is desirable to minimize the amount of damage which might be caused should an immovable object such as a large rock be struck by the teeth of a trench digging chain.
Additionally, the trenching teeth previously used have not been particularly well adapted for carrying loosened dirt upward within a trench being dug by such chain-carried teeth.
What is desired, then, is an improved trench-digging chain which can be utilized in combination with the engine, clutch, and chain bar of a chain saw to dig narrow trenches more efficiently than can be done with a normal wood-cutting saw chain, which may be installed on a chain saw drive unit with a minimum of modification of the drive unit, and whose construction minimizes damage incurred when hard objects are met.